nixos/radicale: give access to /dev/urandom

A git command was failing in the test with

    error: unable to get random bytes for temporary file: Operation not permitted
    error: unable to create temporary file: Operation not permitted
    error: .Radicale.lock: failed to insert into database
    error: unable to index file '.Radicale.lock'

nixos/modules/services/networking/radicale.nix

@@ -164,7 +164,7 @@ in {
         StateDirectoryMode = "0750";
         # Hardening
         CapabilityBoundingSet = [ "" ];
-        DeviceAllow = [ "/dev/stdin" ];
+        DeviceAllow = [ "/dev/stdin" "/dev/urandom" ];
         DevicePolicy = "strict";
         IPAddressAllow = mkIf bindLocalhost "localhost";
         IPAddressDeny = mkIf bindLocalhost "any";